Profile Information

Method Name

NTXUR: VITROS Competitive Chemiluminescence Immunoassay

NTXCT: Enzymatic Colorimetric Assay

Reporting Name

NTX-Telopeptide, U

Specimen Type

Urine

Specimen Required

Patient Preparation: For
24 hours before this urine collection, do not take
multivitamins or dietary supplements containing biotin or vitamin
B7 that are commonly found in hair, skin, and nail supplements and
multivitamins.

Container/Tube: Plastic, 13-mL urine tube

Specimen Volume: 4 mL

Collection Instructions:

1. Collect second morning void.

2. No preservative.

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type

Temperature

Time

Urine

Frozen (preferred)

30 days

Refrigerated

14 days

Ambient

72 hours

Reject Due To

Hemolysis

Mild reject; Gross reject

Lipemia

NA

Icterus

NA

Other

Specimen with pH <5; specimen containing preservatives

Clinical Information

Human bone is continuously remodeled through a process of
osteoclast-mediated bone formation and resorption. This process can
be monitored by measuring serum and urine markers of bone formation
and resorption. Approximately 90% of the organic matrix of bone is
type I collagen, a helical protein that is cross-linked at the N-
and C-terminal ends of the molecule. The amino acid sequences and
orientation of the cross-linked alpha 2 N-telopeptide of type 1
collagen make it a specific marker of human bone resorption.
N-terminal telopeptide (NTx) molecules are mobilized from bone by
osteoclasts and subsequently excreted in the urine. Elevated levels
of NTx indicate increased bone resorption.

Bone turnover markers are physiologically elevated during
childhood, growth, and during fracture healing. The elevations in
bone resorption markers and bone formation markers are typically
balanced in these circumstances and of no diagnostic value. By
contrast, abnormalities in the process of bone remodeling can
result in changes in skeletal mass and shape. Many diseases, in
particular hyperthyroidism, all forms of hyperparathyroidism, most
forms of osteomalacia and rickets (even if not associated with
hyperparathyroidism), hypercalcemia of malignancy, Paget disease,
multiple myeloma, and bony metastases, as well as various
congenital diseases of bone formation and remodeling can result in
accelerated and unbalanced bone turnover. Unbalanced bone turnover,
usually without increase in bone turnover, is also found in
age-related and postmenopausal osteopenia and osteoporosis.

Disease-associated bone turnover abnormalities should normalize
in response to effective therapeutic interventions, which can be
monitored by measurement of serum and urine bone resorption and
formation markers.

Reference Values

All units are reported in nmol Bone Collagen Equivalents/mmol
creatinine.

Adult (≥18 years of age)

Males:

21-83 nmol BCE/mmol creatinine

Females:

Premenopausal: 17-94 nmol BCE/mmol creatinine

Postmenopausal: 26-124 nmol BCE/mmol creatinine

Pediatric

Males:

Tanner Stage I: 55-508 nmol BCE/mmol creatinine

Tanner Stage II: 21-423 nmol BCE/mmol creatinine

Tanner Stage III: 27-462 nmol BCE/mmol creatinine

Tanner Stage IV: <609 nmol BCE/mmol creatinine

Tanner Stage V: <240 nmol BCE/mmol creatinine

Females:

Tanner Stage I: 6-662 nmol BCE/mmol creatinine

Tanner Stage II: 193-514 nmol BCE/mmol creatinine

Tanner Stage III: 13-632 nmol BCE/mmol creatinine

Tanner Stage IV: <389 nmol BCE/mmol creatinine

Tanner Stage V: <132 nmol BCE/mmol creatinine

Interpretation

Most patients with osteopenia or osteoporosis have low, but
unbalanced, bone turnover, with bone resorption dominating over
bone formation. While this may result in mild elevations in bone
turnover markers in these patients, finding significantly elevated
urine NTx levels is atypical. Therefore, if levels are
substantially elevated above the young adult reference range
(>1.5- to 2-fold), the likelihood of coexisting osteomalacia, or
of an alternative diagnosis as described in the Clinical
Information section, should be considered.

When alternative causes for elevated NTx have been excluded in
an osteopenia/osteoporosis patient, the patient must be considered
at increased risk for accelerated progression of
osteopenia/osteoporosis.

A 30% or greater reduction in this resorption marker 3 to 6
months after initiation of therapy indicates a probably adequate
therapeutic response.

The Negotiated Rulemaking Committee of HCFA also recommends:

"Because of significant specimen to specimen collagen crosslink
physiologic variability (15%-20%), current recommendations for
appropriate utilization include: 1 or 2 baseline assays from
specified urine collections on separate days; followed by a repeat
assay about 3 months after starting antiresorptive therapy;
followed by a repeat assay in 12 months; thereafter not more than
annually, if medically necessary."

Day(s) and Time(s) Performed

Monday, Wednesday, Friday; Varies

Analytic Time

1 day

Performing Laboratory

Mayo Medical Laboratories in Rochester

Test Classification

This test has been cleared or approved by the U.S. Food and Drug
Administration and is used per manufacturer's instructions.
Performance characteristics were verified by Mayo Clinic in a
manner consistent with CLIA requirements.